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Obesity associated cancer

February 9, 2021
Overweight and obesity which is defined as abnormal or excessive fat accumulation have reached pandemic levels on a worldwide basis.  According to WHO, around 60–70% of the adult population in developed countries are obese and it is increasing rapidly in developing countries as well. Prevalence of obesity have been associated with increased risk of non-communicable diseases and its comorbidities, such as type-2 diabetes mellitus (T2DM), cardiovascular disease, musculoskeletal disorders etc.
Recent studies have documented a strong association between obesity and certain cancers. Obesity appears to be the third most important risk factor for the development of multiple malignancies and has been linked to thirteen types of cancer, which include:
  • esophageal adenocarcinoma
  • gastrointestinal cancers (colon, gallbladder, stomach, liver, pancreas)
  • renal cell cancer
  • post-menopausal breast cancer
  • ovarian cancer
  • uterus cancer
  • thyroid cancer
  • non-Hodgkin lymphoma
  • multiple myeloma (a type of blood cancer)
  • meningioma (a type of brain tumour)

How obesity increases the risk of cancer?

The link between excess body weight and cancer is complex. According to studies, chronic inflammation, high hormone levels, such as estrogen and leptin, and high insulin in the blood can contribute to cancer. Excess visceral fat deposit in obese individuals also have significant role in triggering the risk of cancer.

The possible mechanisms that obesity is linked with cancer include:

  1. Inflammatory response:

    Due the excessive visceral fat deposits, specialized immune cells called macrophages will act on those fat deposits to remove dead and dying fat cells. Macrophage mediated clearance of the dead adipocyte (fat cells) may be associated with an inflammatory response and the fat cells respond by releasing inflammatory chemicals  known as cytokine. These cytokines act as chemoattractant (which attracts motile cells) for invading cancer cells and facilities cell division.

  2. Sex hormones

    Excess fat cells can trigger the release of significant amounts of estrogen. Estrogen in normal levels is important for sexual and reproductive development. Excess estrogen acts upon other cells and encourage those cells to divide more rapidly which could result in tumor growth. In obese women, excess estrogen is linked to an increased risk for post-menopausal breast, endometrial and ovarian cancers.

  3. Insulin:

    Insulin hormone produced by beta cells of the pancreas is essential for controlling the blood sugar levels. Excess body fat makes the cells resistant to the effects of insulin, thereby the pancreas produces more insulin. Increased levels of insulin and insulin growth factor-1 (IGF-1), over a period of time have significant effect on the levels of growth factors, which triggers the cells to divide. Both insulin and these growth factors promote uncontrolled cell division and may lead to development of cancer.

Preventive measures for obesity associated cancer

For obese people, achieving a sustainable and healthy weight is essential to prevent obesity-related cancers. Lifestyle modifications are considered as the key to prevent obesity. Changes in the quantity, type, and quality of dietary intake, and change in the degree and regular physical activity have significant role in reducing body weight.

Steps that help to manage obesity and obesity-related cancers are:

  • Follow healthy diet: Include fiber-rich foods, such as fruits, vegetables, nuts, whole grains in your diet. Avoid foods that are rich in saturated fats and calories.
  • Stay active: Aim for 150 minutes of moderate activity or 75 minutes of vigorous activity a week.
  • Stay stress free: Practice yoga and other methods to keep yourself calm and relaxed.
  • Stop or limit alcohol intake and smoking: Avoid drinking and cigarette smoking. It can help you to stay fit and maintain a healthy weight.
For those patients who fail to achieve weight loss by these non-surgical means, doctors may consider surgical interventions for effective management of morbid obesity.

Treatment for obesity associated cancer

Obesity or overweight not only increases the risk of developing cancer but also raise serious challenges after a cancer diagnosis. The impact of cancer treatment differs among obese cancer patients and normal cancer patients. Treatment options for obesity associated cancer include:  chemotherapy, radiation therapy and surgery.

  • Chemotherapy in obese patients:It is a treatment option that uses specific drugs to kill or stop the growth of cancer cells. These drugs interfere with the process of cell division and promote cancer cell death. Despite the importance of appropriate dosing for treatment efficacy, up to 40% of obese patients receive limited dosing not based on their body weight [6]. This is because of concerns about toxicity among obese patients if they receive a dose based on their actual body weight. Hence, in most cases, chemotherapy is recommended as an adjuvant therapy after the surgery/ radiation therapy to kill remaining cancer cells
  • Radiation therapy in obese patients:It involves usage of high energy beams to shrink and destroy tumors. X-rays, gamma rays, electron beams, photon beam therapy are common energy beams used in radiation therapy. It can be given alone or in combination with chemotherapy or surgery. Radiation therapy can be given in two ways i.e. externally or internally. More intense radiation is required for obese patients because there is more distance between the tumor and the skin surface.
  • Cancer surgery for obese patients:Surgery involves complete or partial removal of tumours surrounding the affected area. Generally, minimally invasive approach is practiced for cancer surgeries, but for obese patients bigger incisions are required. In obese patients there will be a difficulty in visualizing critical structures using an endoscope. Most of the obese patients develop serious airway complications under general anesthesia. Additionally, they have a higher risk of complications after surgery including heart attack, nerve injury, and wound infection.

Outlook

Obesity is a major risk factor of cancer globally. Women have high risk of developing cancers than men. Maintaining a healthy weight is essential for reducing your risk for cancer. Even though, cancer treatments have their own challenges in obese individuals, it is geared toward positive outcomes. According to studies, individuals who lose weight and maintain healthy lifestyles have significant reduction in cancer incidence and mortality. It offers a ray of hope in obese individuals that losing weight may help them prevent cancer.

References :

  1. How does obesity cause cancer?. https://www.cancerresearchuk.org/health-professional/awareness-and-prevention/obesity-and-cancer-information-for-health-professionals/how-does-obesity-cause-cancer. Accessed on: 04-08-2020.
  2. Basen-Engquist K, Chang M. Obesity and cancer risk: recent review and evidence. Curr Oncol Rep. 2011;13(1):71-76.
  3. Berger NA. Obesity and cancer pathogenesis. Ann N Y Acad Sci. 2014;1311:57-76. doi:10.1111/nyas.12416
  4. Obesity, Weight, and Cancer Risk. https://www.cancer.net/navigating-cancer-care/prevention-and-healthy-living/obesity-weight-and-cancer-risk. Accessed on: 04-08-2020.
  5. How does obesity cause cancer?. https://www.mdanderson.org/publications/focused-on-health/how-does-obesity-cause-cancer. Accessed on: 04-08-2020.
  6. Body fatness, weight gain and cancer. https://www.wcrf.org/dietandcancer/exposures/body-fatness Accessed on: 04-08-2020.
  7. Griggs JJ, Mangu PB, Anderson H, et al. Appropriate chemotherapy dosing for obese adult patients with cancer: American Society of Clinical Oncology clinical practice guideline. J Clin Oncol. 2012;30:1553‐1561..
  8. Ross KH, Gogineni K, Subhedar PD, Lin JY, McCullough LE. Obesity and cancer treatment efficacy: Existing challenges and opportunities. Cancer. 2019 May;125(10):1588-1592.

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Overweight and obesity which is defined as abnormal or excessive fat accumulation have reached pandemic levels on a worldwide basis.  According to WHO, around 60–70% of the adult population in developed countries are obese and it is increasing rapidly in developing countries as well. Prevalence of obesity have been associated with increased risk of non-communicable diseases and its comorbidities, such as type-2 diabetes mellitus (T2DM), cardiovascular disease, musculoskeletal disorders etc.
Recent studies have documented a strong association between obesity and certain cancers. Obesity appears to be the third most important risk factor for the development of multiple malignancies and has been linked to thirteen types of cancer, which include:
  • esophageal adenocarcinoma
  • gastrointestinal cancers (colon, gallbladder, stomach, liver, pancreas)
  • renal cell cancer
  • post-menopausal breast cancer
  • ovarian cancer
  • uterus cancer
  • thyroid cancer
  • non-Hodgkin lymphoma
  • multiple myeloma (a type of blood cancer)
  • meningioma (a type of brain tumour)

How obesity increases the risk of cancer?

The link between excess body weight and cancer is complex. According to studies, chronic inflammation, high hormone levels, such as estrogen and leptin, and high insulin in the blood can contribute to cancer. Excess visceral fat deposit in obese individuals also have significant role in triggering the risk of cancer. The possible mechanisms that obesity is linked with cancer include:
  1. Inflammatory response:
Due the excessive visceral fat deposits, specialized immune cells called macrophages will act on those fat deposits to remove dead and dying fat cells. Macrophage mediated clearance of the dead adipocyte (fat cells) may be associated with an inflammatory response and the fat cells respond by releasing inflammatory chemicals  known as cytokine. These cytokines act as chemoattractant (which attracts motile cells) for invading cancer cells and facilities cell division.
  1. Sex hormones:
Excess fat cells can trigger the release of significant amounts of estrogen. Estrogen in normal levels is important for sexual and reproductive development. Excess estrogen acts upon other cells and encourage those cells to divide more rapidly which could result in tumor growth. In obese women, excess estrogen is linked to an increased risk for post-menopausal breast, endometrial and ovarian cancers.
  • Insulin:
Insulin hormone produced by beta cells of the pancreas is essential for controlling the blood sugar levels. Excess body fat makes the cells resistant to the effects of insulin, thereby the pancreas produces more insulin. Increased levels of insulin and insulin growth factor-1 (IGF-1), over a period of time have significant effect on the levels of growth factors, which triggers the cells to divide. Both insulin and these growth factors promote uncontrolled cell division and may lead to development of cancer.

Preventive measures for obesity associated cancer

For obese people, achieving a sustainable and healthy weight is essential to prevent obesity-related cancers. Lifestyle modifications are considered as the key to prevent obesity. Changes in the quantity, type, and quality of dietary intake, and change in the degree and regular physical activity have significant role in reducing body weight. Steps that help to manage obesity and obesity-related cancers are:
  • Follow healthy diet: Include fiber-rich foods, such as fruits, vegetables, nuts, whole grains in your diet. Avoid foods that are rich in saturated fats and calories.
  • Stay active: Aim for 150 minutes of moderate activity or 75 minutes of vigorous activity a week.
  • Stay stress free: Practice yoga and other methods to keep yourself calm and relaxed.
  • Stop or limit alcohol intake and smoking: Avoid drinking and cigarette smoking. It can help you to stay fit and maintain a healthy weight.
For those patients who fail to achieve weight loss by these non-surgical means, doctors may consider surgical interventions for effective management of morbid obesity.

Treatment for obesity associated cancer

Obesity or overweight not only increases the risk of developing cancer but also raise serious challenges after a cancer diagnosis. The impact of cancer treatment differs among obese cancer patients and normal cancer patients. Treatment options for obesity associated cancer include:  chemotherapy, radiation therapy and surgery. Chemotherapy in obese patients: It is a treatment option that uses specific drugs to kill or stop the growth of cancer cells. These drugs interfere with the process of cell division and promote cancer cell death. Despite the importance of appropriate dosing for treatment efficacy, up to 40% of obese patients receive limited dosing not based on their body weight [6]. This is because of concerns about toxicity among obese patients if they receive a dose based on their actual body weight. Hence, in most cases, chemotherapy is recommended as an adjuvant therapy after the surgery/ radiation therapy to kill remaining cancer cells Radiation therapy in obese patients: It involves usage of high energy beams to shrink and destroy tumors. X-rays, gamma rays, electron beams, photon beam therapy are common energy beams used in radiation therapy. It can be given alone or in combination with chemotherapy or surgery. Radiation therapy can be given in two ways i.e. externally or internally. More intense radiation is required for obese patients because there is more distance between the tumor and the skin surface. Cancer surgery for obese patients: Surgery involves complete or partial removal of tumours surrounding the affected area. Generally, minimally invasive approach is practiced for cancer surgeries, but for obese patients bigger incisions are required. In obese patients there will be a difficulty in visualizing critical structures using an endoscope. Most of the obese patients develop serious airway complications under general anesthesia. Additionally, they have a higher risk of complications after surgery including heart attack, nerve injury, and wound infection.

Outlook

Obesity is a major risk factor of cancer globally. Women have high risk of developing cancers than men. Maintaining a healthy weight is essential for reducing your risk for cancer. Even though, cancer treatments have their own challenges in obese individuals, it is geared toward positive outcomes. According to studies, individuals who lose weight and maintain healthy lifestyles have significant reduction in cancer incidence and mortality. It offers a ray of hope in obese individuals that losing weight may help them prevent cancer.

References :

  1. How does obesity cause cancer?. https://www.cancerresearchuk.org/health-professional/awareness-and-prevention/obesity-and-cancer-information-for-health-professionals/how-does-obesity-cause-cancer. Accessed on: 04-08-2020.
  2. Basen-Engquist K, Chang M. Obesity and cancer risk: recent review and evidence. Curr Oncol Rep. 2011;13(1):71-76.
  3. Berger NA. Obesity and cancer pathogenesis. Ann N Y Acad Sci. 2014;1311:57-76. doi:10.1111/nyas.12416
  4. Obesity, Weight, and Cancer Risk. https://www.cancer.net/navigating-cancer-care/prevention-and-healthy-living/obesity-weight-and-cancer-risk. Accessed on: 04-08-2020.
  5. How does obesity cause cancer?. https://www.mdanderson.org/publications/focused-on-health/how-does-obesity-cause-cancer. Accessed on: 04-08-2020.
  6. Body fatness, weight gain and cancer. https://www.wcrf.org/dietandcancer/exposures/body-fatness Accessed on: 04-08-2020.
  7. Griggs JJ, Mangu PB, Anderson H, et al. Appropriate chemotherapy dosing for obese adult patients with cancer: American Society of Clinical Oncology clinical practice guideline. J Clin Oncol. 2012;30:1553‐1561..
  8. Ross KH, Gogineni K, Subhedar PD, Lin JY, McCullough LE. Obesity and cancer treatment efficacy: Existing challenges and opportunities. Cancer. 2019 May;125(10):1588-1592.